1. Field of the Invention
The invention is related to colored toner used for xerographic duplicators and printers and a preparation method thereof.
2. Description of the Related Art
Colored toner, mainly consisting of resin, pigment, and additive, is an important material for color laser printing and color digital copying. Conventional methods for preparing a colored toner involve melting and mixing a resin (mainly a copolymer of styrene-butyl acrylate), a colorant (a pigment or a dye), and an additive (a charge regulator or a release agent), grinding the mixture mechanically at low temperature, further grinding by gas flow, and grading to yield a colored toner with a particle size of about 10 μm. The methods have difficulty in uniformly dispersing the colorant in the resin, and the resultant toner particles are big and their size and shape are not uniform. Thus, upon printing or copying, the resolution is low, the color is poor, the rate of waste toner is high, and the colored toner is easy to stick to rollers. The suspension polymerization method developed by Canon Co., Ltd. can effectively control the particle size of colored toner, improve the flow and charging properties, enhance the fixation stability and consolidation properties, and inhibit print through. However, the resultant toner has a wide particle size distribution, and upon printing or copying, the resolution is low and the color is poor. In addition, the toner is too round in shape, which makes it very difficult to recycle and clean the residual toner on a photoreceptor.
The emulsion polymerization/co-flocculation method developed by Fuji Xerox and Konica-Minolta can narrow the particle size of colored toner to 5 μm or even a nano level by regulating a surfactant and shear rate and control the shape of colored toner by controlling flocculation and heat treatment, whereby improving the resolution and color of printing and copying. The resultant toner is non-spherical, which makes it easy to recycle and clean the residual toner on a photoreceptor. However, in the process of mixing, flocculating, and heating the polymer emulsion and the colorant emulsion, the resin particles and the colorant particles are hard to disperse uniformly and hard to bind to each other. On the other hand, to improve the anti-partial printing properties, a large amount of wax is required, which easily causes wax to transfer to the surface of toner to pollute the carrier and developing sleeve. Furthermore, excess wax causes the uneven distribution of pigment in the toner, whereby resulting in a poor quality of printing and copying.